This invention relates to paper handling systems, and more particularly, to a duplex copying system that maintains job integrity during duplexing.
Duplex copying systems that employed copy set storage means in the past have used set separators, bottom feeders and duplex return transport means to achieve the duplex function.
Bottom sheet feed devices have been employed as duplex buffer set trays in the past and have included pressurized air to reduce friction between the bottom sheet and the sheet stack tray and minimize friction between the bottom sheet and sheets immediately adjacent thereto.
Problems encountered during the use of such systems included some misfeeding of sheets which reduced reliability of the systems and tended to discourage their use because one would not have an indication when a misfeed occurred and therefore, would not know whether the output of the copier included a complete set of duplexed copies or not.
The present invention is intended to overcome the above-mentioned disadvantages and comprises a system for detecting misfeed of one-sided copy sheets from a duplex tray and includes counting the number of sheets coming into the duplex tray and comparing for coincidence that count with the number of sheets leaving the duplex tray before set separator fingers allow the next set of copies to drop into position to be fed out of the duplex tray. When a complete set or book is counted in the tray, a solenoid is energized which rotates a pair of set separator fingers above the set. Sheets of the following book can now continue to be fed into the tray, at the same time sheets are fed out of the tray. If the machine logic counts the same number of sheets of the first book fed out as was fed in, the fingers will retract to allow the second set to fall into place for feeding. If, however, a double feed has occurred, the logic would not energize the solenoid because a full count had not been reached in the required time and a machine shut-down would occur.